[Effects of taurine on alterations in structure and function of sternohyoid muscle in metabolic syndrome rats].
OBJECTIVE
To investigate the alterations in structure and function of sternohyoid muscle of metabolic syndrome (MS) rats effects and the effects of taurine thereupon contractile properties.


METHODS
Twenty-one healthy male SD rats were randomly assigned to three groups: control group (Group A, n=6) fed with normal food, MS group (Group B, n=8) fed with high-lipid forage for 9 weeks to induce MS and then fed with the same high-lipid forage for 12 weeks in addition, and taurine group (Group C, n=7), fed with high-lipid forage for 20 weeks and given gastric perfusion of taurine 50 mg x d(-1) x kg(-1) since the tenth week for 12 weeks. Venous blood samples were collected to undergo biochemical examination of plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and glucose (Glu). Radioimmunoassay was used to detect the plasma insulin. The sternohyoid muscles were collected. Muscle tissue homogenate was made. The superoxide dismutase (SOD) and malondialdehy (MDA) levels were measured. Myosin-ATPase histochemistry was used to assay the size and capillary density of the isolated sternohyoid muscles. Isometric contractile properties were determined by electrostimulating the strips of isolated sternohyoid muscles at different frequencies (from 10 Hz to 100 Hz) to observe the changes of the sternohyoid contractile properties in different conditions.


RESULTS
(1) The levels of TG, LDL, Glu, PGI, and MDA of Group B were significantly higher than those of Groups A and C, while the HDL level of Group B was significantly lower than that of Group A (P < 0.01). The OD level of Group B was significantly lower than those of Groups A and C. (2) The capillary density, capillary-to-fiber ratio (C/F), and cross-sectional area of type I fiber in sternohyoid muscles of Group B were (140 +/- 5)/ nm2, 0.90 +/- 0.11, and (6119 +/- 165) microm2 respectively, all significantly higher than those of Group A [(278 +/- 17)/mm2, 1.43 +/- 0.05, and (9371 +/- 68) microm2 respectively, all P < 0.01] and Group C [(269 +/- 10)/mm2, 1.40 +/- 0.07, and (9007 +/- 136) microm2 respectively, all P < 0.01]. (3) The tensions of sternohyoid muscle of Group B at the frequencies from 10 Hz to 60 Hz were (29 +/- 6) g/cm2, (34 +/- 7) g/ cm2, (41 +/- 6)g/cm2, (47 +/- 6)g/cm2, (53 +/- 7)g/cm2, and (59 +/- 20)g/cm2 respectively, all significantly lower than those of Group A group[(40 +/- 3)g/cm2, (52 +/- 13)g/cm2, (60 +/- 17) g/cm2, (74 +/- 32) g/cm2, (80 +/- 29)g/cm2, and (96 +/- 24)g/cm2 respectively, all P < 0.05] and Group C [(43 +/- 26)g/cm2, (48 +/- 6)g/cm2,(55 +/- 9)g/cm2, (67 +/- 14)g/cm2, (75 +/- 15)g/cm2, and (80 +/- 15)g/cm2 respectively, all P < 0.05]. (4) In fatigue test, the tension percentages of sternohyoid muscle at the time intervals of 1 min, 2 min, 3 min, 4 min, and 5 min of Group B were (80.5 +/- 8.0)%, (64.1 +/- 1.2)%, (59.1 +/- 1.1)%, (56.4 +/- 10.9)%, and (53.5 +/- 9.1)% respectively, all significantly lower than those of Group A [(87.7 +/- 3.5)%, (78.5 +/- 1.5)%, (76.0 +/- 1.2)%, (72.3 +/- 15.0)%, and (68.7 +/- 17.2)% respectively, all P < 0.05] and Group C group [(87.4 +/- 2.4)%, (77.9 +/- 5.5)%, (73.6 +/- 1.1)%, (71.3 +/- 8.7)%, and (68.0 +/- 6.7) respectively, all P < 0.05].


CONCLUSIONS
With the development of MS, the capillary density, C/F, cross-sectional area of type I fiber of upper airway muscles decrease, in part via oxidative stress, which leads to reduction of the contractile function of upper airway muscles, thus contributing to the onset of obstructive sleep apnea-hypopnea syndrome.
Sun
Xing-hua
XH
Department of Respiratory Medicine, Peking University Third Hospital, Beijing, China.
Zhang
Le-qiang
LQ
He
Bei
B
Li
Feng
F
Tang
Yan
Y
Wang
Jian-dong
JD
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002784:Cholesterol / Q000097:blood; D004041:Dietary Fats / Q000008:administration & dosage; D066298:In Vitro Techniques; D008075:Lipoproteins, HDL / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood / Q000209:etiology / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects*; D009334:Neck Muscles / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D018384:Oxidative Stress / Q000187:drug effects; D011863:Radioimmunoassay; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013654:Taurine / Q000494:pharmacology*; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D004041:Dietary Fats; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D014280:Triglycerides; D013654:Taurine; D002784:Cholesterol